1. Field of the Invention
The invention relates to the field of plasma chambers and in particular to separation of isotopes by using magnetic mirrors in a plasma chamber in combination with improved collectors and plasma sources.
2. Description of the Prior Art
The prior art has devised extensive technologies relating to gaseous diffusion processes to separate isotopes. In addition the prior art has also devised a method for separating isotopes in a neutral dense plasma. In this prior art process, such as described by Dawson, "Isotope Separation by Magnetic Fields," U.S. Pat. No. 4,081,677 (1978), incorporated herein by reference, a neutral mixture of positive and negative ions of a desired product and electrons are injected into a partial vacuum to form a neutral dense plasma in a magnetic field where one of the isotopes of the product is given more energy than the others. The differential energy is imparted by selectively driving the desired isotope at its resonant frequency which is close to, but different from the cyclotron frequency of the other isotope(s). The cyclotron resonant frequency will generally depend upon the plasma density, the relative concentration of electrons if the plasma contains electrons, the strength of the magnetic field, the ratio of a charged mass of a particular isotopes and on various physical parameters of the plasma apparatus itself, such as the ratio of the plasma column length to its radius. The selected isotope is separated for others on the basis of the differential energy imparted to it. The separation is practiced by utilizing the differential diffusion of the ions across a magnetic field or magnetic mirrors may be utilized which confine the more energetic species. Dawson, however, failed to disclose and failed to find any operable mechanism for collecting the confined isotopic species.
Magnetic mirrors are shown in FIGS. 6 and 7 of Dawson in which a magnetic field in a downward direction is shown by arrow 71 and another magnetic field is provided going in an upward direction as shown by arrow 72. The two magnetic areas are separated by field free space 73. FIG. 7 illustrates the path of an ion 76 as it enters space 77. The particle collides at 78 with another particle and its path is changed to a downward spiral illustrated as 80. By subsequent collisions such as shown at 81, the particle moves eventually into the field free space 73 and then into the second magnetic field space 82 eventually to emerge at 83. The diffusion time of particle 76 depends on the Larmor radius, which is the radius of the spiral 80. Each collision of the particle transport the orbit of the ion by up to the diameter of the helix 80. As a result of the collision the particle has a roughly equal probability to move toward the left instead of toward the right. A second such particle is shown at 84. The more energetic species of ion will diffuse across magnetic spaces 77 and 82 more rapidly than the less energetic ions.
A pair of magnetic mirrors can also be used to confine a hotter species between the mirrors, while a cooler, less energetic species flows out of the mirror space as described in connection with FIG. 8 of Dawson. As an ion moves into a mirror region its transverse motion builds up at expense of its longitudinal motion. The effect is stronger the larger the initial transverse motion, i.e. motion perpendicular to the axis of the chamber and lines of the magnetic field. Hence, an ion, which has been heated in a transverse direction, upon reaching the right hand end of the chamber is returned toward the left as shown in 95, because it does not have enough longitudinal energy to pass through the mirror. The path of the less energetic ion is shown at 96. Conversely because this ion has less energy, it has less transverse motion and hence comparatively speaking a larger longitudinal motion. Due to its higher energy in the longitudinal direction, it can escape the magnetic mirror as shown at 97. As a result, the less energetic ions escape the mirror while the more energetic ions are confined between the two mirrors. However, the process of Dawson, called the Calutron process, realized only low isotope purities on the collected or plated product.
Therefore, what is needed are improvements to the Calutron process wherein isotope separation purities may be increased and product output increased.